1. Field of the Invention
The present invention relates to a lithography apparatus and a method of manufacturing an article.
2. Description of the Related Art
A lithography apparatus such as an exposure apparatus for use in the manufacture of a device includes heat generating sources such as a linear motor for driving a positioning table and an electric substrate, so it is important to precisely maintain the internal temperature of the lithography apparatus by suppressing the environmental temperature rise caused by these heat generating sources. If the internal temperature of the lithography apparatus rises (fluctuates), temperature fluctuations of a gas in the optical path of exposure light cause uneven exposure, temperature fluctuations of a gas in the optical path of an interferometer decrease the positioning accuracy, and thermal deformation of a reticle or a substrate such as a wafer occurs. These drawbacks make high-accuracy exposure difficult to perform. Therefore, the lithography apparatus includes a temperature-regulating device for suppressing temperature fluctuations in a chamber and maintaining the internal temperature of the chamber at a predetermined temperature.
In the lithography apparatus as described above, it is necessary to regulate the internal temperature of the chamber with a high resolution, and implement precise positioning while suppressing uneven exposure. Also, the lithography apparatus is required to further increase the throughput (the number of substrates to be processed per unit time (the number of products)), and hence is required to drive the positioning table at a high acceleration. If the acceleration of the positioning table is increased, however, the amount of generated heat of the linear motor also increases, so a high cooling capacity of cooling the linear motor is necessary. As a consequence, recent lithography apparatuses tend to consume high electric power.
The temperature-regulating device for temperature-regulating (cooling) the linear motor generally includes a cooler and heater. This is so because the response of the cooler to control is low, so in order to precisely temperature-regulate the linear motor, it is necessary to cool a medium (liquid or gas) for cooling the linear motor by the cooler, and then heat the medium to a predetermined temperature by the heater (that is, to perform temperature-regulation on the heater side). The cooling capacity of the cooler is generally determined based on the amount of generated heat of the linear motor while the lithography apparatus is in operation. Accordingly, a heater having a heating capacity required to raise the temperature of the medium in accordance with the cooling capacity of the cooler is necessary.
In this temperature-regulating device, the cooling capacity of the cooler is held constant so that the sum total of the amount of generated heat of the linear motor and the heating amount of the heater is constant. When the throughput is high, therefore, the amount of generated heat of the linear motor is maximum, so the heating amount of the heater is decreased. When the throughput is low, the amount of generated heat of the linear motor is smaller than that when the throughput is high, so the heating amount of the heater is increased. In a standby state, the amount of generated heat of the linear motor is minimum, so the heating amount of the heater is maximized. Accordingly, the related art controls the cooling capacity of the cooler to be constant regardless of the throughput or even in the standby state. As a consequence, electric power is wasted when the throughput is low or in the standby state (non-operation state).
As a technique of reducing the power consumption in the non-operation state, therefore, Japanese Patent Laid-Open No. 2003-302088 has proposed a technique which variably controls the cooling capacity of the cooler (the cooling amount of the cooler) by an inverter so as to minimize the heating amount of the heater. This technique reduces the cooling amount of the cooler in the standby state because the amount of generated heat of the linear motor is small, and increases the cooling amount of the cooler in the operation state because the amount of generated heat of the linear motor is large.
In the lithography apparatus, the technique of reducing the power consumption of the temperature-regulating device which temperature-regulates the linear motor for driving the positioning table has been proposed. However, no technique which reduces the power consumption of the linear motor itself for driving the positioning table has been proposed.
This is so because driving of the positioning table in the lithography apparatus has been performed by taking account of only the achievement of maximum productivity. Accordingly, the positioning table is driven at only a maximum acceleration which enables driving by the linear motor (that is, which corresponds to a maximum current which can be output from the motor driver to the linear motor), and the power consumption of the linear motor has not been taken into consideration. Recently, however, demands have arisen for increasing the throughput and reducing the power consumption in the operating state, particularly, the power consumption of the liner motor itself.